This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To investigate the prevalence and familial aggregation of endometriosis in rhesus macaques. Endometriosis occurs in several non-human primate species that have menstrual cycles. Between 1978 and 2002, we identified 144 rhesus macaques with endometriosis. We established a large multigenerational pedigree and nine nuclear families comprising 1,602 females. Prevalence of endometriosis increased with age. Familial aggregation of endometriosis was strongly suggested by a significantly higher average kinship coefficient among affected animals compared with those unaffected. We saw a higher recurrence risk for full siblings when compared to maternal half siblings and paternal half sibs. The segregation ratio among affected mothers was not significantly higher compared with unaffected mothers. The results support familial aggregation of endometriosis in rhesus macaques and indicate that this is a promising animal model for investigating the mode of inheritance, the location of potential genetic susceptibility loci and the influence of environmental factors. Evaluation of pedigree and genetic information is continuing. In the current report period, we isolated DNA from archived and fresh tissue samples for a genome-wide association study. The project is currently expanding to include additional clinical collaborators through our CTSA (see SPID 0447) and a web-based survey of the prevalence of endometrisosis in the colonies of the other NPRCs. This research used WNPRC Animal Services and Aging Resources. Funded by a supplement to RR000167.